Valve positioner according to the input signal is divided into pneumatic valve positioner, electrical valve positioner and intelligent valve positioner. Pneumatic valve positioner input signal is a standard gas signal, for example, 20 ~ 100kPa gas signal, the output signal is also a standard gas signal. Electrical valve positioner input signal is a standard current or voltage signal, for example, 4 ~ 20mA current signal or 1 ~ 5V voltage signal, the electric valve positioner inside the electrical signal into electromagnetic force, and then output gas signal toggle Control valve. The intelligent electric valve positioner converts the current signal output by the control room into a gas signal for driving the regulating valve. According to the friction of the valve stem during working of the adjusting valve, the unbalance force generated by the fluctuation of the medium pressure is offset, so that the valve opening degree corresponds to the control Room output current signal. And intelligent configuration can be set to the appropriate parameters to achieve the purpose of improving control valve performance.
According to the direction of action can be divided into one-way valve positioner and two-way valve positioner. One-way valve positioners for piston actuators operate in one direction only and the two-way valve positioners act on both sides of the piston actuator cylinder in both directions.
According to the valve positioner output and input signal gain symbol is divided into the positive role of the valve positioner and reaction valve positioner. Positive valve positioner input signal increases, the output signal is also increased, so the gain is positive. When the input signal to the reaction valve positioner increases, the output signal decreases, so the gain is negative.
Press the valve positioner input signal is an analog signal or digital signal can be divided into ordinary valve positioner and fieldbus electrical valve positioner. Common valve positioner input signal is analog pressure or current, voltage signal, field bus electrical valve positioner input signal is the field bus digital signal.
Whether the valve positioner with CPU can be divided into ordinary electric valve positioner and intelligent electric valve positioner. Ordinary electric valve positioners do not have a CPU and, therefore, are not intelligent and can not handle the intelligence involved. Intelligent electric valve positioner with CPU, can handle the intelligent operations, for example, can be non-linear compensation for the forward channel, fieldbus electrical valve positioner with PID and other functional modules, to achieve the appropriate operation.
According to the feedback signal detection method can also be classified.
For example, the use of mechanical linkage valve position signal detection valve positioner: Hall effect displacement detection method to detect valve stem displacement valve positioner: Electromagnetic induction method to detect stem displacement of the valve positioner.
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